We had a similar problem naming our two.....and its weird because when they arrive and you actually see them, any names you originally thought of dont seem right.
Eg . No 1 - Boy
We had some names in mind but, when we looked at him we thought 'looks like bloody trouble' so called him William (Will for short).....and its definately apt!
No 2 - Girl
Named her Katerine (kate for short), and shes a bugger (alcoholic) to!
Funnily, for us, the longer names work as you call them Will and Kate most (some!) of the time but, when thier naughty you revert to the long name.......and then they know they are in trouble

So my advice, get some ideas and consider what it might be shortened to, what the initilials spell (we knew a Chris Rumble who was forever getting post address to Mr Crumble), is it a piss take name (i.e. any characters on Tv that may distract i.e. Vicky Pollard) and how it works with the surname (we know a Harris Pole.....poor little bugger, particularly at election time!)...........but dont be afraid to change it if it really does not suit them when they arrive!